The invention concerns a method for regulation of ventilation as well as an air-conditioning device used in the method.
A method for regulation of ventilation is known wherein the indoor air is circulated so that at least a portion of the indoor air, a so-called return-air portion, is mixed with the outdoor air passed into the room. The proportion of outdoor air can be regulated within the range of 0 to 100 percent, i.e., in extreme cases, either all the air passed into the room consists of outdoor air or of recirculated return air.
In the prior-art, traditional mixing-regulation methods, generally, three dampers are used such that at least two dampers are interconnected mechanically or electrically such that, when the return-air damper is opened, the outdoor-air damper and the waste-air damper are closed to a corresponding extent. The possible changes in the turning angles of the dampers are within the range of 0 . . . 90.degree..
A problem in the prior-art mixing ventilation methods and in the apparatus used in these methods has been the poor controllability of the inlet and outlet air flows. The control of the mixing ratio and of the mixing degree has not been adequate. The inlet and outlet air flows have been changed by as much as 30 percent while the mixing ratio of outdoor air and return air has been changed within the range of 0 . . . 100 percent. Moreover, in the prior-art methods and apparatuses, it has not been possible to define or, thus, to control the mixing ratio of outdoor air to return air. For example, if it has been desired that the ratio of outdoor air to return air is 1/3, in reality this ratio has been 2/1. In such a case, the amount of outdoor air has been a multiple of the desired amount of outdoor air. Moreover, the overall inlet air quantity has still been 20 to 30 percent larger than the desired overall air quantity. A situation of the sort described above causes a considerable variation in the pressure ratios in an air-conditioning plant as well as a significant increase in the energy requirements.
The mixing of outdoor air and return air, i.e. their mixing degree, has also been problematic in the prior-art air-conditioning methods and apparatuses. When attempts have been made to mix warm return air and cold outdoor air, the mixed air, however, remains in layers so that the warm air flows in the upper portion of the duct and the cold air in its lower portion. This causes problems in particular in a heating radiator, because in such a case the bottom portion of the radiator tends to be frozen.
In traditional embodiments of mixing units, it has become a further problem that, with higher proportions of return air, the inlet and outlet air blowers become connected in series from the point of view of air flow. This causes an increase in the amounts of air both in the inlet-air ducts and in the outlet-air ducts. An increase in the amounts of air causes an increase in the speed of rotation of the blower and, consequently, of its motor, and thereby an increase in the amount of electric current used by the blower. When certain limit values of electric current are exceeded, the over-current protection switches are activated and the whole system stops.